1. Field of the Invention:
The present invention relates in general to opening/closing mechanisms for doors and the like and more specifically to means for supervising the integrity of a pneumatic safety system used with such opening/closing mechanisms.
2. Description of the Related Art:
A somewhat typical prior art industrial door opening/closing mechanism is somewhat diagrammatically shown in FIG. 1 wherein a door A is slidably supported by a support track B for being moved by a motorized drive unit C between opened and closed positions relative to an opening D. A hollow, compressible pneumatic nose E is attached to the leading edge of the door A for coacting with a typical pressure switch F to either deactivate the drive unit C or cause the drive unit C to reverse and open the door A if something causes the nose E to compress when the door A is closing.
A preliminary patentability search directed to class 49, subclasses 26, 27, 28 and 31; class 200, subclass 61.43; and class 340, subclass 605 resulted in the discovery of Walter, U.S. Pat. No. 4,365,188. The Walter patent discloses a circuit arrangement for monitoring and controlling closing and opening movements utilizing a hollow, compressible nose including a pair of elongated switch strips to thereby define an electric switch.
None of the known prior art, taken as a whole, disclose or suggest the present invention.